The invention relates to a method of conforming to varying parameters a selected electric control current which is being supplied to a pressure regulating valve and is memorized with additional control currents in, and can be addressed and read out from, a characteristic field in dependency upon prevailing operating conditions to serve as an actual control current.
The invention further relates to apparatus for the practice of the above outlined method.
Automation of gear shifting transmissions in the power trains of motor vehicles is gaining in popularity on several grounds including an enhancement of the comfort to the occupant(s) of the motor vehicle as well as a reduction of specific fuel consumption. One of the reasons that an automatic or automated gear shifting transmission can bring about savings in fuel consumption is that one can drive more frequently in a relatively long gear; this causes the average pressure of a combustion engine to rise and its specific fuel consumption to drop.
In accordance with a simplified automation of the power train of a motor vehicle, only the clutch is automated whereas the transmission is shifted by hand. Owing to the thus enhanced shifting comfort, the operator of the motor vehicle is more likely to shift, and to shift more frequently, into so-called long gears which brings about a reduction of fuel consumption for reasons already pointed out hereinbefore.
If the power train of a motor vehicle employs a fully automatic transmission, it is of advantage (in order to achieve savings in fuel consumption) to operate with a starter clutch in lieu of with a torque converter clutch. In order to avoid excessive slip and the need for the application of very high fluid pressures, the operation of such starter clutches must be regulated with a rather high degree of accuracy. In other words, all such operational parameters (including torque, RPM and/or others) of the power train which influence the starting and the operation of hydraulic systems being utilized to operate automated clutches must be ascertained and processed with a very high degree of precision. As already mentioned above, such undertakings must ensure that the automated clutch can operate without excessive slip as well as that the hydraulic fluid being utilized to operate various units (such as cylinder-and-piston units) of the clutch need not be subjected to relatively high or very high pressures.
It is customary to employ a pressure regulating valve (e.g., a proportionally operating pressure regulating pilot valve) as a means for determining the pressure of a suitable hydraulic fluid (such as oil) which is being conveyed to and advanced from the fluid-operated components of the automated clutch. It is also known to employ a control unit having a memory for the storage of a characteristic field with information denoting a plurality of control currents serving as desired or required currents for the operation of the pilot valve under certain specific (selected) circumstances of operation of the power train. Once the proper control current in the characteristic field of the memory has been addressed, it is thereupon utilized as the desired or required current to control the adjustment (setting) of the pilot valve in order to achieve the aforementioned objects, such as savings in fuel and avoidance of the need for control fluids having very high or extremely high pressures.
In accordance with a presently known proposal, the above outlined objects or requirements concerning adjustments of the pilot valve which regulates the pressure of hydraulic fluid flowing to various hydraulically operated units of an automated clutch can be accomplished in a simple manner by storing the information which is contained in the characteristic field in the memory of the control unit in the following way: Each fluid pressure change of a predetermined magnitude brings about or corresponds to a predetermined change of control current. The changes of control current are dependent upon the selected desired regulating current, i.e., upon the respective desired pressure and the respective temperature.
The above outlined proposal is satisfactory under ideal circumstances, e.g., if one disregards changes which develop due to progressing wear upon the constituents of the power train, manufacturing tolerances, changes in the consistency and/or other parameters of the hydraulic fluid and/or deposits of foreign matter in the fluid and/or upon the mechanical constituents of the prime mover. It has been ascertained that the just enumerated (and certain other) unpredictable changes in or departures from optimum conditions can greatly and adversely influence the operation of conventional control units which regulate the pressure of fluid being supplied to the cylinder-and-piston units and/or to other hydraulically operated components of automated clutches in the power trains of motor vehicles. In other words, presently known control units and the information stored in the memories of such control units cannot ensure the absence of slip (or excessive slip) in the automated clutch and/or excessive fuel consumption if the characteristics of the aforementioned unpredictable parameters depart from optimum values. Excessive departures of actual control or regulating pressure from the desired or required pressure can greatly affect the operation of the automated clutch as well as of the entire power train.
An object of the invention is to provide a method of regulating the pressure of hydraulic fluid being supplied to and by a fluid pressure regulating valve for use in or in conjunction with automated clutches in such a way that the quality of operation of the automated clutch is not affected (or is not unduly affected) by departures of actual fluid pressures from optimum fluid pressures in spite of progressing wear upon the mechanical parts, pronounced manufacturing and/or assembling tolerances, changes in the quality of the hydraulic fluid and/or others.
Another object of the invention is to provide a method which ensures highly satisfactory operation of the automated clutch for extended portions of useful life of the power train.
A further object of the invention is to provide a method which can be practiced by resorting to a relatively simple electronic control unit as well as to available signal generating and signal transmitting monitoring devices.
An additional object of the invention is to provide a power train wherein the operation of the automated clutch can be regulated in accordance with the above outlined method.
An additional object of the invention is to provide a method which renders it possible to avoid (or at least reduce) hysteresis in the hydraulic characteristic curve of a valve for the regulation of a consumer of a pressurized hydraulic fluid.
Still another object of the invention is to reduce the differences between the actual value and the desired or required value of the pressure of hydraulic fluid being supplied to one or more cylinder-and/piston units and/or other fluid-operated constituents of automated transmissions in the power trains of motor vehicles.
A further object of the invention is to provide a method which can be resorted to in connection with the operation of power trains in motor vehicles as well as under numerous other circumstances when the pressure of hydraulic fluid being supplied to or being discharged by a pressure regulating valve must be controlled with a high or extremely high degree of accuracy under circumstances when progressing wear, manufacturing and/or assembly tolerances and/or changes in the composition of hydraulic fluid can and normally do greatly influence the operation of heretofore known and utilized pressure regulating systems.
An additional object of the invention is to provide an apparatus for the practice of the above outlined method.
Another object of the invention is to provide a relatively simple, compact, reliable and long-lasting apparatus for controlling the operation of pressure regulating valves in the power trains forming part of motor vehicles and employing automated clutches and/or transmissions.
Still another object of the invention is to provide a novel and improved combination of an electronic control unit and one or more sensors which monitor the pressure, the temperature, the torque, the wear, the RPM and/or other variables that are likely or bound to adversely influence the accuracy of operation of pressure regulating valves in the power trains of motor vehicles and/or under numerous other circumstances of use.
One feature of the present invention resides in the provision of a method of conforming to varying parameters a selected electric control current which is being supplied to a fluid pressure regulating valve (e.g., to an electromagnet of such valve) and is memorized with additional control currents as a desired control current in and is withdrawable (e.g., addressible) from a characteristic field in a memory, as a function of prevailing operating conditions, to serve as an actual control current. The improved method comprises the steps of (a) superimposing upon one of the actual control current and a modulating current having a predetermined amplitude the other of the actual control current and the modulating current, (b) ascertaining a pressure amplitude which is brought about by the modulating current, (c) comparing the ascertained amplitude with a predetermined pressure amplitude, and (d) correcting (in a sense to reduce the extent of the aforementioned departure) the characteristic field upon detection of a departure of ascertained amplitude from the predetermined amplitude.
The electric control current can be supplied from an outlet of a control circuit to an input of a clutch pressure regulating valve.
The modulating current is (or can be) an alternating current, and the superimposing step can include superimposing the modulating current upon the selected actual control current in the course of several periods, and such method can further comprise the step of averaging the amplitudes of signals being transmitted by a fluid pressure sensor during the aforementioned several priods. The correcting step can be carried out as a function of the amplitide of the averaged signal.
The improved method can also comprise the step of determining correction values for at least two different pressures being regulated by the pressure regulating valve.
The arrangement can be such that the correcting step can be carried out only if during the superimposing step the desired control current changes by less than a predetermined value.
The superimposing step can be carried out at different temperatures.
The pressure regulating valve can be installed in a power train of a motor vehicle; under such circumstances, the regulating valve can constitute a clutch regulating valve, and the power train can comprise a manually shiftable change-speed transmission.
The memory can form part of an electronic control circuit which is arranged to receive signals from a plurality of sensors for transmitting to the control circuit signals denoting changes of various parameters of constituents of a motor vehicle.
Another feature of the invention resides in the provision of an apparatus for conforming to varying parameters an electric control current for at least one fluid pressure regulating valve. The improved apparatus comprises a fluid pressure regulated actuating arrangement (such as at least one constituent of a prime mover in a motor vehicle) which is regulated by the pressure of fluid being supplied by the at least one valve, a plurality of sensors which are arranged to monitor different variable parameters of the actuating arrangement and to transmit signals denoting the variations of the respective parameters, and a control unit having inputs for signals from the sensors and including at least one memory for a characteristic field of fluid pressure changes, an output connected to a current-consuming element of the at least one valve, and means for modifying memorized pressure changes in response to signals from the sensors.
The actuating arrangement can include a clutch, such as an automated clutch in the power train of a motor vehicle; such power train can further comprise a manually shiftable transmission.
The sensors can include at least one pressure monitoring sensor, at least one temperature monitoring sensor and/or at least one RPM monitoring sensor. Furthermore, at least one of the sensors can be set up to monitor the rate of fuel admission to the prime mover of a motor vehicle.
The modifying means of the control unit can include means for modifying memorized pressure changes in a stepwise fashion and, if desired and/or necessary, in a succession of stages.
The modifying means can comprise means for comparing the memorized pressure changes with required pressure changes reflecting the signals from one or more sensors and for modifying the memorized pressure changes when the comparison indicates the existence of predetermined differences between the memorized pressure changes and the required pressure changes. The means for modifying can be arranged to modify memorized pressure changes in a sense to reduce the differences between the modified pressure changes and the required pressure changes.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and the mode of assembling the same and the methods which can be practiced therewith, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.